flat-key-patch

Overview ¶

Package main demonstrates flat dotted-key JSON patching with go-codex.

Some JSON formats use flat dotted keys instead of nested objects:

{
  "properties.desired.modules.my-container":    {"image": "...", "status": "running"},
  "properties.desired.modules.other-container": {"image": "...", "status": "running"},
  "properties.desired.schemaVersion":           "1.0"
}

This pattern is common in Azure IoT Edge device twins, Kubernetes ConfigMaps with dot-separated keys, and flat namespaced configuration stores.

The example shows ten patterns:

1. Fixed dotted key — codex.RequiredField with a dotted Name literal.
2. Dynamic key via [File.Patch] — build the key with string concatenation.
3. Typed update via [PatchEncoded] + codex.StringMap — validates values.
4. Key + value validation via [PatchEncoded] + codex.Map — validates both.
5. Adding new keys not in the file codec — field survival via patchCodec.
6. Schema rendering — twinCodec, moduleCodec, modulePatchCodec as OpenAPI YAML.
7. Error cases + structured logging — FileEncodeError, FileDecodeError, FileReadError.
8. Observer summary — per-operation metrics collected by FileMetricsObserver.
9. Key+value merge with codex.EntrySlice (single field) — decode flat object into []Container where container name is extracted from the key.
10. Multi-field key extraction — two segments (tenant + name) extracted from the key into a struct using a codex.Struct domain codec + codex.MapCodecValidated.
11. Static key — the container name is a compile-time constant, not a wire value. codex.MapCodecSafe injects the constant into the decoded struct; encode drops it.

Run with: go run ./examples/flat-key-patch